1. Field of the Invention
This invention is directed to crystalline aluminosilicate zeolites and to a method of preparing same wherein crystalline aluminosilicate zeolites of high purity are crystallized in the form of large particles having an ultimate crystal size greater than about one micron, that is from about 1 micron to 2 microns or larger. ZSM-5 catalysts having the above-described crystal size are highly useful in selective toluene disproportionation and methanol conversion processes and other selective aromatics conversion processes.
2. Description of the Prior Art
ZSM-5 crystalline aluminosilicate zeolites are well known in the art, being particularly described in U.S. Pat. No. 3,702,886, the entire contents of which are incorporated herein by reference; and although large particle ZSM-5 type zeolites have previously been prepared, such processes have generally not been commercially viable procedures. It was previously thought that ultimate zeolite crystal size was predominantly dependent on the nature of the reaction mixture employed. It has now been discovered that crystal size is also significantly affected by the rate of addition of the organic compound, that is, its effective concentration in the crystallization media, and the temperature and pH conditions and the degree of agitation of the crystallization medium.